This is a front-end for the Online Encyclopedia of Integer Sequences, made by Christian Perfect. The idea is to provide OEIS entries in non-ancient HTML, and then to think about how they're presented visually. The source code is on GitHub.
%I A136813 #9 Apr 12 2024 18:11:45
%S A136813 0,1,10,11,100,101,110,111,1000,1001,1010,1011,1100,1101,1110,10000,
%T A136813 10001,10010,10011,10100,10101,10110,10111,11000,11001,11010,11100,
%U A136813 11101,100000,100001,100010,100011,100100,100101,100110,100111,101000,101001,101010,101011,101100,101110,110000,110001,110010,110100,110101,111000,111001,111010
%N A136813 Numbers k such that k and k^2 use only the digits 0, 1, 2, 3 and 7.
%C A136813 Generated with DrScheme.
%H A136813 Jonathan Wellons, <a href="/A136813/b136813.txt">Table of n, a(n) for n = 1..1411</a>
%H A136813 J. Wellons, <a href="https://web.archive.org/web/20090206165028/http://jonathanwellons.com/shared-digits/">Tables of Shared Digits</a> [archived]
%e A136813 3711303010100^2 = 13773770032777320702010000.
%t A136813 With[{c={0,1,2,3,7}},Select[FromDigits/@Tuples[c,6],SubsetQ[c,IntegerDigits[#^2]]&]] (* _Harvey P. Dale_, Apr 12 2024 *)
%K A136813 base,nonn
%O A136813 1,3
%A A136813 Jonathan Wellons (wellons(AT)gmail.com), Jan 22 2008